The desire for a greater economy with a very good drivability requires a better adaptation of the vehicle operating conditions in motor vehicles to the most advantageous operating ranges of a driving engine. This is achieved by means of multi-speed or continuously variable transmissions having a great transmission range. In order to exploit the advantages, the speeds of the transmission should be optimally changed or shifted, which places high demands on the driver. If the continuously variable transmission is treated as a transmission with infinite speeds, the considerations that are valid for continuously variable transmissions can be transferred similarly, as a rule, also to multi-speed transmissions. For purposes of simplicity, reference will be made in the following embodiments especially to a multi-speed transmission and the terminology compatible therewith.
In order to relieve the driver and increase riding comfort, more and more vehicles are being offered with a fully automated transmission consisting of an engine, a starter element, for example a clutch and/or a converter, a transmission with different gear ratios and a drive axle with wheels. Part of the automation consists in selecting an advantageous gear ratio for the respective operating condition of the vehicle and determining the correct shifting point. Economy and riding comfort should be taken into consideration at the same time.
Known automatically shifting step-by-step variable gears for motor vehicles are shifted automatically within the range of available speeds primarily depending upon speeds that are proportional to the driving speed and upon load conditions, for example, the position of an accelerator pedal or throttle pedal during idle, partial load, full load or kickdown. In order to reduce the number of shifting operations, the driver can exclude speeds in the upper or lower range from the shifting sequence via a selector switch, for example, while ascending a mountain or during winter operation.
Also known are systems in which the microprocessor electronics determine the speed to be shifted in accordance with a predetermined computer program. If a high shifting characteristic or kickdown is reached in the shifting characteristic field, the electronics trigger a corresponding shifting operation. The torque of the engine is reduced during the shifting operation in order to burden the friction elements less and improve shifting comfort. Several programs having different shifting diagrams are provided for different driving situations. The shifting can occur automatically between the individual shifting diagrams. It is also possible to adapt the shifting characteristics in dependence upon operating parameters.
Multi-speed transmissions, which are shifted with an interruption of the tractive force, are frequently used for utility vehicles. A control device for automatically shifting multi-speed, step-by-step variable gears is known, for example, from EP 0 255 519 B1, in which the shifting points are fixed in dependence upon the vehicle speed, the torque requirement (throttle lever position) and the acceleration determined from the speeds of the gearbox output shaft.
The throttle pedal position is further divided into three regions, namely, into an idle region, a central region and a full load region. To each region of the throttle pedal position is allocated an acceleration region so that under these prerequisites eighteen shifting points result. The shifting conditions for the shifting points are retained in tables wherein the values are determined empirically or by calculation. Several tables may be needed, depending on the number of running programs that are utilized.
From DE 197 03 561 A1, a device for evaluating vehicle, driving and operating parameters is known, which makes a selection of gear ratios available and can be utilized as a standard for different automatically shifting transmissions and requires a low synchronization effort. This device serves for evaluating the vehicle, driving and operating parameters of a vehicle, in order to select and adjust a gear ratio of a transmission by means of a microprocessor in accordance with specific algorithms, parameters or characteristic diagrams, wherein an acceleration of the vehicle is determined by calculation from the change of the driving speed corresponding to the speed of a power train with an engine and a transmission.
The devices for evaluating vehicle, driving and operating parameters of a vehicle that are known from the state of the art, which select and adjust a gear ratio of a transmission by means of a microprocessor in accordance with predetermined algorithms, parameters, or characteristic diagrams, have a disadvantage that they do not take into consideration among the influence parameters any of the changes subjected to durability or service life. Gear selection thus occurs based on evaluation criteria that refer to the new condition, and not the changes in the transmission and on the vehicle caused by the operation.
It is the object of the present invention to outline a device for evaluating vehicle, driving and operating parameters of a vehicle, which evaluates a gear ratio of a transmission according to predetermined algorithms, parameters, or characteristic diagrams, while taking into consideration specific transmission criteria and parameters; selects and adjusts the same by means of a microprocessor. The gear selection occurs, in particular, based on the evaluation criteria, which take into consideration the changes in the transmission and on the vehicle caused by the operation.